1. Field of Invention
This invention pertains to the art of aircraft that can transport substantial amounts of cargo, and more particularly, to lighter than air (LTA) aircraft that can perform this function.
2. Description of the Related Art
Jet cargo planes have developed as one way to transport large amounts of cargo. For example, the 707 freighter was introduced by Boeing around 1977. Boeing has more recently introduced the 747. The 747 was designed to serve as an all-cargo transport. 747's are able to carry 100 tons (90,000 kg) of cargo.
Lighter than air (hereafter "LTA") airships are generally known, but their ability to successful transport substantial amounts of cargo has, until now, been limited. U.S. Pat. No. 4,052,025 discloses a large semi-buoyant lift-augmented aircraft. The Jul. 24, 1974 issue of "Aviation Week & Space Technology" discloses a hybrid heavy-lift, semi-lighter than air vehicle dubbed the Megalifter. The American Institute of Aeronautics and Astronautics' conference held in Snowmass, Colo. on Jul. 15-17, 1975 resulted in the AIAA Paper No. 75-930 which discloses "An Evaluation of Advanced Airship Concepts." This paper discloses multiple LTA aircrafts.
Lighter-than-air aircraft have been proposed by companies such as CargoLifters of Germany. Historically, these aircraft only use static lifting to create lift. Static lifting refers to lift created by lighter than air gasses, such as helium, in the aircraft. These make the airship buoyant, thereby providing static lift. However, because only static lift is used, these LTA have been capable of carrying only light payloads in relation to their size. The current invention utilizes dynamic lift as well as static lift and is therefore able to carry substantially heavier payloads. Dynamic lifting refers to lift created by air rushing over the wings of an aircraft.
LTA aircraft of the related art have not utilized dynamic lift because the structure of these aircraft could not withstand the forces created by dynamic lift. Because the airships were not sufficiently rigid, potential deformation of the fuselage did not permit the use of dynamic lift. The extreme forces exerted on the fuselage would cause it to collapse. Additionally, the designs of the related art are not as safe or stable as the current invention. Moreover, the current invention can carry heavier payloads and is less expensive to manufacture, operate and maintain than the historical LTA airships of the related art.
Typically, to provide static lift, the LTA aircraft of the related art, have used a constant differential pressure envelope to contain the buoyant gas. LTA aircraft or blimps such as the Goodyear blimp as operated by the Goodyear Tire & Rubber Co., modulate their volume of helium according to altitude and temperature. They have systems that allow the blimp to "inhale and exhale" in order to keep the volume and the shape of the airfoil constant. Balloonetts are commonly used for this purpose. The balloonetts also keep ambient air away from the helium, which prevents mixing and contaminating the helium. The ballonets units have very low operating ceilings, because pressure and altitudes pressure changes can effect the shape of the fuselage and lift. For these reasons, these systems do not offer promise for meeting the demand of transporting heavy volumes of goods.
A previous commercially available LTA airship was the giant Zeppelin Hindenburg built approximately 1937. This was an airship capable of lifting 230 tons. However, for such blimps to provide such lifting capabilities, these structures, that utilize only static lift, must be mammoth. This immense size, however, presents great problems and disadvantages. Atmospheric forces, such as wind, will force such an airship to fight a constant battle for direction. To counter such forces, the propulsion systems must be powerful. However, powerful propulsion systems are typically heavy and result in inefficient fuel usage. Additionally, these vector thrust type propulsion systems are typically cumbersome and have many mechanical difficulties.
For the foregoing reasons, the current state of the art does not offer promise for meeting the demand of transporting heavy volumes of goods. To solve such problems, a new type of aircraft has been developed. This aircraft utilizes dynamic as well as static lift to stow and transport cargo. This aircraft provides the means to achieve a constant envelope, allowing pressure to vary with altitude and temperature without compromising the structural integrity of the fuselage. Other means are used to achieve inherent stability and enhanced maneuverability, both in flight and on the ground. Higher altitudes can be achieved and a variety of missions can be provided when these types of characteristics are achieved. Safety factors can be achieved by protecting the internal helium cells.